As the air transport industry has developed, so have regulations on what goods are transportable by air and how those goods are to be packaged for air shipment. One concern of the air transport industry, as well as the various governmental entities worldwide which control this industry, is the air shipment of potentially harmful or destructive materials, for example, corrosive, poisonous, flammable, toxic and volatile materials.
The International Air Transport Association (i.e., IATA) has specified a number of standards for the shipment of such materials. The standards specified by this organization have been generally adopted by the United Nations and are enforced by many governments worldwide. The U.S. has adopted standards which are similar, if not identical, to the IATA standards. One of the goals of the IATA standards is to prevent the leakage of such potentially harmful or destructive materials from their shipping containers into the environment of the transporting aircraft. With this goal in mind, the 1992 IATA standards Paragraph 5.0.2.9 requires that these materials be shipped in containers capable of withstanding an internal pressure of about 14 psi without the container leaking its contents, whether liquid or in vapor form. Presently, the U.S. only requires enforcement of this container leaking standard on international shipments and not domestically. However, it is predicted that the U.S. will require this standard for domestic shipments in the near future.
Such potentially harmful or destructive materials are often shipped in regular paint can-type containers, with press fit or friction resealable lids. While these containers are adequate to store such materials when shipped by land, they have been found generally inadequate for shipment by air. These materials are generally volatile in nature, and produce their own vapor pressure when stored in such containers. These containers are usually filled at around sea level under about one atmosphere of pressure (i.e., around 14 psi). When the containers are in the air during transport, the pressure outside the container drops because of the altitude while the pressure inside remains relatively unchanged. This pressure differential, along with the vapor pressure due to the volatile nature of these materials, can cause vapors to leak out of the container. Depending on the nature of the material being stored, these vapors can have a variety of detrimental effects on the aircraft structure itself, other goods being shipped and personnel on the aircraft, as well as those who unload the aircraft.
While containers themselves can be specially designed for shipping these potentially harmful or destructive materials by air, such special containers are often more expensive than standard paint can-type containers. In addition, many manufacturers of these materials ship their product by land, as well as by air. Thus, it is desirable for these manufacturers to have one standard container for their product which can be used regardless of whether shipment is by land or air. Standard paint can-type containers are relatively inexpensive. Therefore, there is a need for an apparatus which would prevent materials from leaking out of such standard paint can-type containers during shipment by air, and which is relatively inexpensive compared to using containers which have been especially designed for air transport.